Process for the oxidation of alcohol



Patented Apr. -17, 1928.

UNITED STATES PATET OFFICE...

STEFAN GQLDSCHMIDT, OF KARLSR'UHE, GERMANY.

PROCESS FOR THE (liiIDA'JPIOIbl' F ALCOHOL.

No Drawing. Application filed December 16, 1927, Serial No. 240,611,, and in Germany November 12, 1926.

The present invention relates to a process of oxidizing ethylalcohol to acetaldehyde and acetic acid.

It is known that alcohol vapour can be oxidized'by passing it, together with air or oxygen, over a catalyst, such as copper or silver.- There are thus produced in addition to water and acetaldehyde acetic acid, methane, acetals and the like. It has not been possible heretofore to conduct the oxidation in such a manner that a good yield of acetaldehyde and acetic acid can be'obtained while the formation of less-valuable by-products is avoided or reduced to aminimum. In fact, no industrial production of acetaldehyde and acetic acid in. this manner has been adopted.

This invention is based on the observation that very good yields of the valuable products, acetaldehyde and acetic acid, are obtained if silver is the catalyst and the latter is maintained at a temperature not below 380 C. and not above 440 (3., advantageously between 400 Guand' 420 C. These 2!! narrow limits must be observed if good yields are to be obtained,

Further, gases leaving the catalyst should i be immediately chilled, so that further changes in the mixture may be avoided. 80 The following examples illustrate'the invention: I

Ewample 1.

Air at 50 C. is passed through alcohol of 96 per cent strength until it is approximately saturated with alcohol vapour and.

the mixture is passed over or' through a silver wire gauze, which has been preheated, at such a speed that the temperature of this 40 catalyst remains constant between 408 and 410 C. For exa'ct measurement of the temperature a part. of the catalyst is wrapped firmly around the thermocouple. 65 per cent of the alcohol is in this manner converted into acetic aldehyde and acetic acid, 31.5 per cent being recovered.

Instead/of a wire netting the catalyst may consist of silver deposited upon a carrier,

such as asbestos.

If the temperature is allowed to exceed that named, the yield falls. At'454 C. the total yield in aldehyde, acid and alcohol was only 77 per cent. J When the heat of the reaction, owing to too slow a passage of the gases or to another proportion between the constituents of t-lfe gases or other dimensions of the apparatus, is not sufficient to maintain the temperature between the proper limits, the gases or the catalyst may be separately heated. For in stance, the air or the mixture of air and alcohol vapour may wholly or in part be preheatedby using for instance the heat of the reaction on the counter-current system. In the latter case, however, care must be taken that there is rapid chilling of the vapours and gases which have left the catalyst.

It has further been found that for the purpose of obtaining a good yield of oxidation products it is convenient to use such a proportion of air (oxygen) to the alcohol which 1t carries, that a pretty thorough utilization of the oxygen occurs in the reaction.

. p Ewampl'e 2.

A mixture of air and vapour of alcohol of 96 per cent strength is made, such that it contains oxygen amounting to only 80 per cent in excess of that necessary for converting all the alcohol into acetaldehyde. By maintaining a temperature of reaction of 428 C. the yield, calculated on the quantity of alcohol used, amounted to 22.3 per cent of unchanged alcohol and 70.8 per cent of aldehyde and acetic acid, so that the totalyield, having regard to 4 per cent of water in the alcohol' of 96 per cent strength, amounted to 97.1 per cent, which must be regarded as a good result.

When the operation is conducted with a larger excess of oxygen, the yield in aldehyde and acetic acid is strongly reduced.- Thus. at 405 Cfand with a. 3- to 5-fold excess of oxygen under the same conditions as are given in this example, only about 38 per cent of aldehyde and acetic acid was ob-' tained, without any further destruction of, the alcohol. 1' I It'has proved to be advantageous to ad just the temperature known to be appro- 100 priate for the catalyst by exact regulation of the speed of current of the gas mixture. In this way may be corrected most conveniently the oscillations of temperature which occur from one cause or another during the cat- 10a alytic process. The adjustment is also possible by varying the proportion between the oxygen and indifierent gas when using air or the like.

- When one uses, as already stated, a comparatively small excess of air (oxygen), apart from the advantage of having a small er quantity of exit gases to cool, there is the advantage that there may be more latitude of temperature between the limits according to the invention without danger of diminishing the yield than when a higher excess of oxygen is used. Thus, at 435 C. only a quite slightly poorer yield of the alcohol (calculated on the quantity of aldehyde, acetic acid and recovered alcohol) is obtained than at a temperature of 410 C.

It is also possible to work with such a proportion of air (oxygen) as is theoretically smaller than is necessary to convert the whole of the alcohol present into aldehyde and acetic acid.

That a less satisfactory yield of aldehyde and acetic acid is obtained with excess of oxygen is surprising. it would have been expected on the contrary that there would be a better conversion of the alcohol, for instance a production of a larger proportlon of acetic acid. The opposite is, however, the case since the yield in altered alcohol falls considerably.

The process may be conducted also at a lower pressure or a higher pressure than that of the atmosphere.

What I claim is:

1. A process for oxidizing etliylalcohol to acetaldehyde and acetic acid with the use of silver as a catalyst and of a mixture of ethylalcohol and air, wherein the oxidatlon occurs at a temperature of the catalyst of 380-440 C.

2. A process for oxidizing ethylalcohol to acetaldehyde and acetic acid with the use of silver as a catalyst and of a mixture of ethylalcohol and-air, wherein the oxidation occurs at a temperature of the catal st ,of

. 380440 C. and wherein. the proportion of 5. Process according to claim 1 wherein the heat of the reaction is used for preheatmg the gases or the catalyst or both.

6. Process according to claim 2 wherein the heat of the reaction is used for preheat ing the gases or the catalyst or both.

7. Process according to claim l'wherein the temperature of the catalyst is controlled by adjusting the speed of the current of gases passing over it.

8. Process according to claim 2 wherein the temperature of the catalyst is controlled meager normal pressure.

10. Process according to claim 2 wherein.

the reaction is conducted under other than normal pressure.

11. Process according to claim 1 wherein the gases of reaction are quickly chilled after they have left the catalyst and wherein the heat of the reaction is used for preheating the gases or the catalyst or both.

12. Process according to claim 2 wherein the gases of reaction are quickly chilled after they have left the catalyst and wherein the heat of the reaction is used for preheating the gases or the catalyst or both.

13. Process according to claim 1.wherein the temperature of the catalyst is controlled by adjusting the speed of the current of gases passing over it and wherein the gasesof reaction are quickly chilled after they have left the catalyst.

14.- Process according to claim 2'wherein the temperature of the catalyst is controlled by adjusting the speedof the current of gases passing over it and wherein the gases of reaction are quickly chilled after they have left the catalyst.

15. Process according to claim 1 wherein the temperature of the catalyst is controlled by, adjusting the speed of the current of gases passing over it and wherein the heat of reaction is used for preheating the gases or thecata'lyst or hot j i 16. Process according to claim 2 wherein the temperature of the catalyst is controlled by adjusting the speed of the current of gases passing .over it and wherein the heat of reaction is used for preheating the gases or the catalyst or both.

17. Process according to claim 1 wherein the temperature of the catalyst is controlled by adjusting the speed of the current of gases passing over it and wherein further the gases of reaction are quickly chilled after they have left the catalyst and the heat of reaction is used for preheating the gases or the catalyst or both.

' 18. Process according to claim 2 wherein n the temperature of the catalyst is controlled by adjusting the speed of the current of gases passing over it and wherein further the ases of reaction are quickly chilled after they have left the catalyst and the heat of reaction is used for preheating the gases or the catalyst or both. I j

I In witness whereof I have hereunto signed my name this 2 day of Dec., 1927. r

" STEFAN GOLDSCHMIDT. 

